JP2020107868A - Organic electroluminescent element and manufacturing method thereof - Google Patents

Abstract

To provide an organic electroluminescent element which can be produced by a coating method and is excellent in current efficiency and light emission life.SOLUTION: In an organic electroluminescent element having a light emitting layer between a pair of electrodes, the light emitting layer includes at least one electron transporting compound, at least one hole transporting compound, and at least one wide gap compound having a HOMO-LUMO energy gap of 3.3 eV or more, and the electron transporting compound is a compound selected from the compound group (1), and/or the hole transporting compound is a compound selected from the compound group (2).SELECTED DRAWING: None

Description

The present invention relates to an organic electroluminescence device and a method for manufacturing the same.

In recent years, an organic electroluminescence display device (hereinafter, also simply referred to as “organic EL display device”) has attracted attention as a next-generation flat panel display device. This organic EL display device is a self-luminous display device that can be thinned, has excellent visibility and viewing angle characteristics, and has low power consumption, and therefore, demand is increasing.

This organic EL display device generally has a plurality of organic electroluminescence elements (hereinafter, also simply referred to as “organic EL element”). Each of the plurality of organic EL elements includes a first electrode formed on the substrate, an organic layer having a light emitting layer formed on the first electrode, and a second electrode formed on the organic layer. There is. Then, by applying an electric field, in the organic layer, the holes injected from the first electrode and the electrons injected from the second electrode are recombined, and the light emitting material forming the organic layer emits light. ing.

In addition, the organic layer generally includes a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, an electron injection layer, and the like.

Here, the organic electroluminescent material used for the organic layer (hereinafter, also simply referred to as “organic EL material”) can greatly affect the luminous efficiency and the luminous life of the organic EL element. Therefore, an organic EL material that can achieve high efficiency and long life of the organic EL element has been researched.

For example, Patent Document 1 proposes an organic EL device in which a light emitting layer is formed from an electron transporting host and two types of triphenylene hosts by a vapor deposition method. Further, Patent Document 2 proposes an organic EL device by a vapor deposition method in which a light emitting layer forming an exciton complex is formed from an electron transporting host and a hole transporting host.

In the production of an organic EL element, it is common to form an organic film forming the organic EL element by a dry film forming method such as a vapor deposition method. On the other hand, since film formation by a dry film formation method such as vapor deposition takes time and cost, instead of such a dry film formation method, a solution coating method capable of suppressing time and cost (hereinafter, simply referred to as “coating method”). It is also considered to use a wet film forming method.

U.S. Patent Application Publication No. 2016/0093808 JP, 2012-186461, A

However, when the organic EL element is formed by a wet film forming method such as a solution coating method, the organic EL material used for vapor deposition is difficult to dissolve in the coating solvent. Further, after the film formation, aggregation of organic molecules in the light emitting layer is likely to occur. Therefore, the organic EL element formed by the coating method has a problem that sufficient luminous efficiency and luminous lifetime are not obtained.

Therefore, it is an object of the present invention to provide an organic electroluminescence device which can be manufactured by a coating method and is excellent in light emission efficiency and light emission life.

The present inventors have conducted earnest research to solve the above problems. As a result, they have found that the above problems can be solved by an organic electroluminescent device having a light emitting layer containing three types of host compounds having a specific structure, and have completed the present invention.

That is, according to one embodiment of the present invention, there is provided an organic electroluminescence device having a light emitting layer between a pair of electrodes, wherein the light emitting layer comprises at least one electron transporting compound and at least one hole. A transportable compound and at least one wide gap compound having a HOMO-LUMO energy gap of 3.3 eV or more,
Provided is an organic electroluminescent device, wherein the electron transporting compound is a compound selected from the following compound group (1), and/or the hole transporting compound is a compound selected from the following compound group (2). To do.

Ar in the compound group (1) and the compound group (2) are each independently a substituted or unsubstituted aryl group or a substituted or unsubstituted heteroaryl group.

In addition, according to another embodiment of the present invention, there is provided a method of manufacturing the organic electroluminescent device.

According to the present invention, there is provided an organic electroluminescence device which can be manufactured by a coating method and is excellent in light emission efficiency and light emission life.

It is a schematic diagram which shows the organic electroluminescent element which concerns on one Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described in detail. The present invention is not limited to the following embodiments.

The present invention is an organic electroluminescence device having a light emitting layer between a pair of electrodes, wherein the light emitting layer is at least one electron transporting compound, at least one hole transporting compound, and HOMO-LUMO. At least one wide gap compound having an energy gap of 3.3 eV or more,
The electron transporting compound is a compound selected from the following compound group (1), and/or the hole transporting compound is a compound selected from the following compound group (2), which is an organic electroluminescent device. ..

Ar in the compound group (1) and the compound group (2) are each independently a substituted or unsubstituted aryl group or a substituted or unsubstituted heteroaryl group.

The organic electroluminescence device of the present invention having such a structure can be produced by a coating method and is excellent in light emission efficiency and light emission life.

The reason why the above-mentioned effects are obtained by the organic electroluminescence element of the present invention is not clear, but the following mechanism is considered.

That is, when three kinds of host compounds having different characteristics are mixed and used in a state where phase separation does not occur, the HOMO level and LUMO level become smooth, and the charge injection barrier is reduced. In addition to this, the adjustment of the charge mobility can be controlled by the mixing ratio of the host compound, so that a high-performance device structure can be achieved.

The above mechanism is based on speculation, and its correctness does not affect the technical scope of the present invention.

Hereinafter, the electron transporting compound, the hole transporting compound, and the wide gap compound contained in the light emitting layer according to the invention will be described in order. In the present specification, the electron transporting compound is also simply referred to as “ET-Host” and the hole transporting compound is also simply referred to as “HT-Host”. The wide gap compound is also simply referred to as "WG-Host". Furthermore, the electron transporting compound, the hole transporting compound, and the wide gap compound are collectively referred to as “host compound”.

According to one embodiment of the present invention, the electron transporting compound is a compound selected from the above compound group (1), and/or the hole transporting compound is a compound selected from the above compound group (2). is there. The above “or” means that (a) the electron transporting compound is a compound selected from the compound group (1), and (b) the hole transporting compound is selected from the compound group (2). It means that one of the forms of the compound is satisfied. Further, the above "and" means that (a) the electron transporting compound is a compound selected from the compound group (1), and (b) the hole transporting compound is selected from the compound group (2). It means that both of the forms of the compound are satisfied. From the viewpoint of further improving the effect of the present invention, it is preferable to satisfy both the forms (a) and (b).

<Electron transport compound (ET-Host)>
The electron transporting compound according to the present invention is preferably a compound selected from the following compound group (1) from the viewpoint of efficiently exhibiting the effects of the present invention.

In the above compound group (1),
Ar is each independently a substituted or unsubstituted aryl group or a substituted or unsubstituted heteroaryl group.

In the present specification, the term “substituted or unsubstituted” means that the substituent and the like may have a substituent other than a hydrogen atom and a deuterium atom. Further, these substituents may be bonded to each other to form a ring. Furthermore, in the present specification, “independently” means that the respective substituents may be the same or different.

The electron-transporting compounds can be used alone or in combination of two or more. The electron-transporting compound may be a commercially available product or a synthetic product.

The aryl group capable of forming Ar in the compound group (1) is not particularly limited, but is a monovalent group containing at least one aromatic hydrocarbon ring having 6 to 30 carbon atoms (aromatic hydrocarbon ring group). ) Is preferable. When the aromatic hydrocarbon ring group contains two or more rings, the two or more rings may be condensed with each other. Further, it may be in the form of a hydrocarbon ring assembly group in which two or more rings are directly bonded by a single bond.

Aromatic hydrocarbon constituting the aromatic hydrocarbon ring group is not particularly limited, but specifically, benzene, pentalene, indene, naphthalene, anthracene, azulene, heptalene, acenaphthalene, phenalene, fluorene, spirobifluorene, Phenanthrene, biphenyl, o-terphenyl, m-terphenyl, p-terphenyl, quaterphenyl, 1,3,5-triphenylbenzene, kinkphenyl, sexiphenyl, septiphenyl, triphenylene, pyrene, chrysene, picene, perylene, Examples include pentaphene, pentacene, tetraphene, hexaphene, hexacene, rubicene, trinaphthylene, heptaphene, pyrantrene and the like.

The heteroaryl group that can form Ar is not particularly limited, but is an aromatic heterocycle having 3 to 30 ring-forming atoms, which has one or more heteroatoms and the remaining ring atoms are carbon atoms (C). A monovalent group (aromatic heterocyclic group) containing one or more of is preferable. When the aromatic heterocyclic group contains two or more rings, the two or more rings may be condensed with each other. Moreover, one or more hydrogen atoms present in these aromatic heterocyclic groups may be substituted with a substituent.

Examples of the hetero atom include a nitrogen atom (N), an oxygen atom (O), a phosphorus atom (P), a sulfur atom (S), and the like. It is preferably a nitrogen atom (N).

Here, the number of ring-forming atoms represents the number of atoms constituting the ring itself in a compound having a structure in which atoms are cyclically bonded (for example, a monocycle, a condensed ring, a ring assembly). When the atom that does not form a ring (for example, a hydrogen atom that terminates a bond of an atom that forms a ring) or the ring is substituted with a substituent, the atom included in the substituent is not included in the number of ring-forming atoms. For example, the carbazolyl group has 13 ring atoms.

Specific examples of the aromatic heterocyclic ring constituting the aromatic heterocyclic group include, for example, pyridine, pyrazine, pyridazine, pyrimidine, triazine, quinoline, isoquinoline, quinoxaline, quinazoline, naphthyridine, acridine, phenazine, benzoquinoline, benzoisoquinoline, Phenanthridine, phenanthroline, benzoquinone, coumarin, anthraquinone, fluorenone, furan, thiophene, benzofuran, benzothiophene, dibenzofuran, dibenzothiophene, pyrrole, indole, carbazole, imidazole, benzimidazole, pyrazole, indazole, oxazole, isoxazole, benzoxazole , Benzisoxazole, thiazole, isothiazole, benzothiazole, benzisothiazole, imidazolinone, benzimidazolinone, imidazopyridine, imidazopyrimidine, imidazophenanthridine, benzimidazophenanthridine, azadibenzofuran, azacarbazole, azadibenzothiophene , Diazadibenzofuran, diazacarbazole, diazadibenzothiophene, xanthone, thioxanthone and the like.

As described above, one or more hydrogen atoms present in the aromatic hydrocarbon ring group and the aromatic heterocyclic group may be substituted with a substituent. Specific examples of the substituent include, for example, a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 30 carbon atoms, a substituted or unsubstituted 6 or 30 carbon atoms. The following aryloxy groups, substituted or unsubstituted secondary or tertiary amino groups having 1 to 30 carbon atoms, cyano groups, substituted or unsubstituted aryl groups having 6 to 30 carbon atoms, or substituted or non-substituted Examples thereof include a substituted heteroaryl group having 3 to 30 ring-forming atoms.

Specific examples of the triazine compound represented by formula 1-A include the following compounds.

In the triazine compound represented by the general formula 1-A, it is more preferable that the three Ars bonded to the triazine ring have different structures from each other. With such a structure, the crystallinity of the compound can be reduced and the solubility of the compound can be increased.

Specific examples of the compounds represented by the general formulas 1-B, 1-C, 1-D, and 1-E include triazine ring, pyrimidine ring, pyridazine ring, and pyrazine ring in the exemplified compound of general formula 1-A. , And compounds in which the pyridine ring is replaced with each other.

Specific examples of the quinazoline compounds and quinoline compounds represented by the general formulas 1-F and 1-G include the following compounds. In addition to them, compounds exemplified by the general formula 1-A in which the triazine ring is replaced with a quinazoline ring or a quinoline ring are also exemplified.

Specific examples of the phosphine oxide compound represented by the general formula 1-H include the following compounds.

The following compounds may be mentioned as specific examples of the anthracene compound represented by General Formula 1-I.

Specific examples of the tetracene compound represented by General Formula 1-J include the following compounds.

Specific examples of the tetraphene compound represented by the general formula 1-K include the following compounds.

From these electron-transporting compounds, it is preferable to select an appropriate material from the viewpoint of the type of dopant, emission color and the like.

Preferred electron-transporting compounds for green phosphorescence are the following ET-Host-AF.

More preferable electron transporting compounds for green phosphorescence are the following ET-Host-E or ET-Host-F compounds.

The content of the electron transporting compound in the host compound is preferably 10% by mass or more and 80% by mass or less, and more preferably 25% by mass or more and 60% by mass or less, with the total mass of the host compound being 100% by mass. More preferable.

In particular, from the viewpoint of further improving the current efficiency, the content of the electron transporting compound in the host compound is preferably 30% by mass or more and 50% by mass or less, with the total mass of the host compound being 100% by mass. From the viewpoint of further improving durability, the content of the electron transporting compound in the host compound is preferably 35% by mass or more and 55% by mass or less, with the total mass of the host compound being 100% by mass.

<Hole-transporting compound (HT-Host)>
The hole transporting compound according to the present invention is preferably a compound selected from the following compound group (2) from the viewpoint of efficiently exhibiting the effects of the present invention.

In the above compound group (2),
Ar is each independently a substituted or unsubstituted aryl group or a substituted or unsubstituted heteroaryl group.

The description of the aryl group and heteroaryl group that can form Ar in the compound group (2) is the same as that described in the section of the electron transporting compound, and therefore the description thereof is omitted here.

The hole transporting compounds can be used alone or in combination of two or more. As the hole-transporting compound, a commercially available product or a synthetic product may be used.

Specific examples of the hole transporting compound include the following compounds.

Among these hole transporting compounds, the following compounds HT-Host-A to D are preferable from the viewpoint of solubility in the solvent used and hole injectability. More preferably, it is the compound of HT-Host-A or HT-Host-B described below.

The content of the hole transporting compound in the host compound is preferably 10% by mass or more and 80% by mass or less, and more preferably 20% by mass or more and 60% by mass or less, with the total mass of the host compound being 100% by mass. ..

<Wide gap compound (WG-Host)>
The wide gap compound according to the present invention is a compound having a HOMO-LUMO energy gap (Eg) of 3.3 eV or more. When the HOMO-LUMO energy gap (Eg) is less than 3.3 eV, the effect of extending the life obtained by applying the wide gap compound as a host material is deteriorated. The upper limit of the HOMO-LUMO energy gap (Eg) is not particularly limited, but is preferably 4 eV or less.

The wide gap compounds can be used alone or in combination of two or more kinds. The wide gap compound may be a commercially available product or a synthetic product.

From the viewpoint of efficiently exhibiting the effects of the present invention, the wide gap compound is preferably a compound selected from the following compound group (3).

In the above compound group (3),
Ar _{1 s} are each independently a hydrogen atom, a substituted or unsubstituted aryl group, or a substituted or unsubstituted monovalent nitrogen-containing heterocyclic group provided that two Ar _{1 s} are simultaneously hydrogen atoms. Not,
Ar ₂ is each independently a phenyl group, a hydrocarbon ring assembly group in which a plurality of aromatic hydrocarbon rings are directly bonded by a single bond, or a substituted or unsubstituted heteroaryl group,
Ar ₃ is each independently a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heteroaryl group,
Ar ₄ is a hydrogen atom, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heteroaryl group.

The substituted or unsubstituted aryl group that can form Ar ₁ , Ar ₃ and Ar ₄ is the same as described above, and the description thereof is omitted here. Further, the substituted or unsubstituted heteroaryl group that can form Ar ₂ , Ar ₃ , and Ar ₄ is also the same as above, and the description thereof is omitted here.

The substituted or unsubstituted monovalent nitrogen-containing heterocyclic group that can form Ar ₁ has 3 or more and 30 or less ring-forming atoms having at least one nitrogen atom and having no sulfur atom or oxygen atom. A monovalent group (nitrogen-containing heterocyclic group) containing at least one nitrogen-containing heterocycle. When the nitrogen-containing heterocyclic group contains two or more rings, the two or more rings may be fused with each other. Moreover, one or more hydrogen atoms present in the nitrogen-containing heterocyclic group may be substituted with a substituent. Specific examples of the substituents are the same as the examples described for the aromatic hydrocarbon ring group and the aromatic heterocyclic group.

Specific examples of the nitrogen-containing heterocyclic ring constituting the nitrogen-containing heterocyclic group include pyridine, pyrazine, pyridazine, pyrimidine, triazine, quinoline, isoquinoline, quinoxaline, quinazoline, naphthyridine, acridine, phenazine, benzoquinoline, benzoisoquinoline, phenanthene. Examples thereof include lysine, phenanthroline, pyrrole, indole, carbazole, imidazole, benzimidazole, pyrazole, indazole, imidazopyridine, imidazopyrimidine, imidazophenanthridine, benzimidazophenanthridine, azacarbazole and diazacarbazole.

The hydrocarbon ring assembly group that can form Ar ₂ is a monovalent group in which a plurality of aromatic hydrocarbon rings are directly bonded by a single bond. Examples of the aromatic hydrocarbon ring include benzene, pentalene, indene, naphthalene, anthracene, azulene, heptalene, acenaphthalene, phenalene, fluorene, spirobifluorene, phenanthrene, biphenyl, o-terphenyl, m-terphenyl, p. -Terphenyl, quaterphenyl, kinkphenyl, sexiphenyl, septiphenyl, triphenylene, pyrene, chrysene, picene, perylene, pentaphene, pentacene, tetraphene, hexaphene, hexacene, rubicene, trinaphthylene, heptaphene, pyrantrene and the like. The plurality of aromatic hydrocarbon rings may be the same or different. Moreover, one or more hydrogen atoms present in the aromatic hydrocarbon ring may be substituted with a substituent. Specific examples of the substituents are the same as the examples described for the aromatic hydrocarbon ring group and the aromatic heterocyclic group.

The alkyl group that can form Ar ₃ is not particularly limited, but is preferably a linear or branched alkyl group having 1 to 30 carbon atoms, for example. Specifically, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, n-pentyl group, isopentyl group, tert-pentyl group, Neopentyl group, 1,2-dimethylpropyl group, n-hexyl group, isohexyl group, 1,3-dimethylbutyl group, 1-isopropylpropyl group, 1,2-dimethylbutyl group, n-heptyl group, 1,4- Dimethylpentyl group, 3-ethylpentyl group, 2-methyl-1-isopropylpropyl group, 1-ethyl-3-methylbutyl group, n-octyl group, 2-ethylhexyl group, 3-methyl-1-isopropylbutyl group, 2 -Methyl-1-isopropyl group, 1-tert-butyl-2-methylpropyl group, n-nonyl group, 3,5,5-trimethylhexyl group, n-decyl group, isodecyl group, n-undecyl group, 1- Methyldecyl group, n-dodecyl group, n-tridecyl group, n-tetradecyl group, n-pentadecyl group, n-hexadecyl group, n-heptadecyl group, n-octadecyl group, n-nonadecyl group, n-eicosyl group, n- Examples thereof include a heneicosyl group, an n-docosyl group, an n-tricosyl group, and an n-tetracosyl group. Of these, a linear or branched alkyl group having 1 to 8 carbon atoms is preferable.

One or more hydrogen atoms present in the alkyl group may be substituted with a substituent. Specific examples of the substituents are the same as the substituents described for the aromatic hydrocarbon ring group and the aromatic heterocyclic group. However, it is not substituted with an alkyl group.

Specific examples of the triphenylene compound represented by formula 3-A include the following compounds.

Specific examples of the dibenzofuran compound represented by the general formula 3-B include the following compounds.

In the dibenzofuran compound represented by the general formula 3-B, it is more preferable that the two Ar _{2 s} bonded to the dibenzofuran ring have different structures from each other. With such a structure, the crystallinity of the compound can be reduced and the solubility of the compound can be increased.

Specific examples of the dibenzothiophene compound represented by formula 3-C include the following compounds.

The following compounds may be mentioned as specific examples of the fluorene compound represented by the general formula 3-D.

Specific examples of the dicarbazole compound represented by the general formula 3-E include the following compounds.

Among these wide-gap compounds, in the Examples, the following WG-Host-, from the compatibility with the coating solvent to be used and the emission color, the compatibility with the electron-transporting compound, the hole-transporting compound, the dopant material, etc. used in combination. AF were selected as preferred compounds.

More preferred are the following WG-Host-A, WG-Host-D, or WG-Host-E compounds.

More preferably, it is the compound of WG-Host-A or WG-Host-D described below.

The content of the wide-gap compound in the host compound is preferably 15% by mass or more and 40% by mass or less, more preferably 16% by mass or more and 35% by mass or less, with the total mass of the host compound being 100% by mass. preferable.

The above-mentioned host compound according to the present embodiment has high solubility in a solvent and can be easily formed into a film (formed into a thin film) by a wet coating method. Further, the organic EL device having the light emitting layer containing the above-mentioned host compound can improve the light emission efficiency and the light emission life even when manufactured by a wet coating method (solution coating method).

[Organic electroluminescence element (organic EL element)]
Hereinafter, the organic electroluminescent element (organic EL element) according to the present embodiment will be described in detail with reference to FIG. FIG. 1 is a schematic diagram showing an organic EL element according to this embodiment. However, the structure of the organic EL element according to this embodiment is not limited to the form shown in FIG.

As shown in FIG. 1, the organic EL device 100 according to the present embodiment includes a substrate 110, a first electrode 120 disposed on the substrate 110, and a hole injection layer 130 disposed on the first electrode 120. A hole transport layer 140 disposed on the hole injection layer 130, a light emitting layer 150 disposed on the hole transport layer 140, an electron transport layer 160 disposed on the light emitting layer 150, and an electron transport layer. The electron injection layer 170 is disposed on the electrode 160, and the second electrode 180 is disposed on the electron injection layer 170.

The light emitting layer 150 of the present embodiment is formed by applying a light emitting layer forming composition containing a host compound and a solvent and drying. That is, the present invention includes at least one electron transporting compound, at least one hole transporting compound, at least one wide gap compound having a HOMO-LUMO energy gap of 3.3 eV or more, and a solvent. A method for producing an organic electroluminescent device, comprising: applying a composition containing, and the electron-transporting compound is a compound selected from the above compound group (1), and/or the hole-transporting compound. The organic compound is a compound selected from the above compound group (2), and a method for producing an organic electroluminescent device is provided.

<Light emitting layer forming composition>
The composition for forming a light emitting layer according to this embodiment is used for forming a light emitting layer of an organic EL element by a coating method. Such a composition for forming a light emitting layer contains the host compound according to the present invention and a solvent.

Any solvent can be used without limitation as long as it can dissolve the host compound. Specifically, for example, toluene, xylene, ethylbenzene, ethylbenzene, diethylbenzene, mesitylene, propylbenzene, cyclohexenyl, cyclohexylbenzene, cyclohexylbenzene, cyclohexylbenzene, cyclohexylbenzene, cyclohexylbenzene. Anisole, ethoxytoluene, phenoxytoluene, isopropylbiphenyl, dimethylanisole, phenylacetate, phenylpropionate, phenylpropionate, phenylpropionate. Examples thereof include methyl benzoate) and ethyl benzoate. These solvents can be used alone or in combination of two or more.

The amount of solvent used is not particularly limited. However, from the viewpoint of ease of coating and the like, the concentration of the host compound is preferably 0.1% by mass or more and 10% by mass or less, more preferably 0.5% by mass or more and 5% by mass or less.

Specific examples of the solution coating method include a spin coat method, a casting method, a micro gravure coat method, a gravure coat method, a bar coat method, and a roll. Roll coat method, wire bar coat method, dip coat method, spray coat method, screen printing method, flexographic printing method, offset (offset) method. ) Printing methods, ink jet (ink jet) printing methods, and the like.

The composition for forming a light emitting layer is applied to form a coating film, and then the coating film is dried to form a light emitting layer.

The method of forming the layers other than the light emitting layer is not particularly limited. The layers other than the light emitting layer may be formed by, for example, a vacuum vapor deposition method or a solution coating method.

As the substrate 110, a substrate used in a general organic EL element can be used. For example, the substrate 110 may be a semiconductor substrate such as a glass substrate, a silicon substrate, or a transparent plastic substrate.

The first electrode 120 is formed on the substrate 110. The first electrode 120 is specifically an anode and is formed of a metal, an alloy, a conductive compound, or the like having a large work function. For example, the first electrode 120 includes indium tin oxide (In ₂ O ₃ —SnO ₂ :ITO), indium zinc oxide (In ₂ O ₃ —ZnO), tin oxide (SnO ₂ ), and oxide that are excellent in transparency and conductivity. It may be formed as a transmissive electrode by zinc (ZnO) or the like. Further, the first electrode 120 may be formed as a reflective electrode by laminating magnesium (Mg), aluminum (Al), or the like on the transparent conductive film.

The hole injection layer 130 is formed on the first electrode 120. The hole injection layer 130 is a layer that facilitates injection of holes from the first electrode 120, and is specifically formed to have a thickness of 10 nm or more and 1000 nm or less, more specifically 10 nm or more and 100 nm or less. Good.

The hole injection layer 130 can be formed using a known hole injection material. Examples of a known hole injection material forming the hole injection layer 130 include, for example, triphenylamine-containing polyether ketone (poly(ether ketone)-containing triphenylamine:TPAPEK) and 4-isopropyl-4′-methyldiphenyliodonium tetrakis. (Pentafluorophenyl)borate (4-isopropyl-4'-methyldiphenyliodonium tetrakis(pentafluorophenyl)borate:PPBI), N,N'-diphenyl-N,N'-bis-[4-(phenyl-m-tolyl-amino) -Phenyl]-biphenyl-4,4'-diamine (N,N'-diphenyl-N,N'-bis-[4-(phenyl-m-tolyl-amino)-phenyl]-biphenyl-4,4'- diamine:DNTPD), copper phthalocyanine (copper phthalocyanine), 4,4′,4″-tris(3-methylphenylphenylamino)triphenylamine (4,4′,4″-tris(3-methylphenylphenylamino)triphenylamine:methylene). -MTDATA), N,N'-di(1-naphthyl)-N,N'-diphenylbenzidine (N,N'-di(1-naphthyl)-N,N'-diphenylbenzylzine:NPB), 4,4'. ,4"-tris(diphenylamino)triphenylamine (4,4',4"-tris(diphenylamino)triphenylamine:TDATA), 4,4',4"-tris(N,N-2-naphthylphenylamino) Triphenylamine (4,4',4"-tris(N,N-2-naphthylphenylamine)triphenylamine:2-TNATA), polyaniline/dodecylbenzenesulfonic acid (polyaniline/dodecylbenzenesulphonic acid), poly(3,4-ethylenediene) Oxythiophene)/poly(4-styrene sulfonate) (poly(3,4-ethylenedioxythiophene)/poly(4-styrene sulfonate), PEDOT-PSS), and polyaniline/10-camphorsulfonic acid (polyaniline/10-camphorsulf). onic acid) and the like.

The hole transport layer 140 is formed on the hole injection layer 130. The hole transport layer 140 is a layer having a function of transporting holes, and may be formed to have a thickness of 10 nm or more and 150 nm or less, for example.

The hole transport layer 140 can be formed using a known hole transport material. Known hole transport materials include, for example, 1,1-bis[(di-4-tolylamino)phenyl]cyclohexane (1,1-bis[(di-4-tolylamino)phenyl]cyclohexane:TAPC), N-. Carbazole derivatives such as phenylcarbazole and polyvinylcarbazole, N,N'-bis(3-methylphenyl)-N,N'-diphenyl-[1,1-biphenyl]-4 ,4'-diamine (N,N'-bis(3-methylphenyl)-N,N'-diphenyl-[1,1-biphenyl]-4,4'-diamine:TPD), 4,4',4" -Tris(N-carbazolyl)triphenylamine (4,4',4"-tris(N-carbazolyl)triphenylamine:TCTA), and N,N'-di(1-naphthyl)-N,N'-diphenylbenzidine (N,N'-di(1-naphthyl)-N,N'-diphenylbenzenezine:NPB) etc. can be mentioned.

In addition, the hole transport materials described in WO 2011/159872, US Patent Application Publication No. 2016/0315259, etc. can also be used.

The light emitting layer 150 is formed on the hole transport layer 140. The light emitting layer 150 is a layer that emits light by fluorescence, phosphorescence, or the like. The light emitting layer 150 includes the host compound according to the present embodiment and is formed by the coating method as described above. The light emitting layer 150 may be formed with a thickness of 10 nm or more and 60 nm or less, for example.

The light emitting layer 150 may include a hole transporting compound (HT-Host) or an electron transporting compound (ET-Host) other than the host compound according to the present embodiment. Examples of such other compounds include, for example, tris(8-quinolinolato)aluminum (tris(8-quinolinato)aluminum:Alq ₃ ),4,4′-bis(carbazol-9-yl)biphenyl(4,4 '-Bis(carbazol-9-yl)biphenyl:CBP), poly(n-vinylcarbazole) (poly(n-vinylcarbazole):PVK), 9,10-di(naphthalen-2-yl)anthracene (9, 10-di(naphthalene) anthracene (ADN), 4,4',4"-tris(N-carbazolyl)triphenylan (4,4',4"-tris(N-carbazolyl)triphenylamine:TCTA), 1, 3,5-Tris(N-phenylbenzimidazol-2-yl)benzene (1,3,5-tris(N-phenyl-benzimidazol-2-yl)benzene:TPBI), 3-tert-butyl-9,10 -Di(naphth-2-yl)anthracene (3-tert-butyl-9,10-di(naphth-2-yl) anthracene: TBADN), distyrylarylene (DSA), 4,4'-bis( 9-carbazole)-2,2'-dimethyl-biphenyl (4,4'-bis(9-carbazole)2,2'-dimethylbiphenyl:dmCBP) and the like.

The light emitting layer 150 preferably contains a fluorescent light emitting compound or a phosphorescent light emitting compound as a dopant material. Specific examples of the fluorescent compound include, for example, perylene and its derivative, rubrene and its derivative, coumarin and its derivative, pyrene and its derivative, 4-dicyanomethylene-2. Examples include -(p-dimethylaminostyryl)-6-methyl-4H-pyran (4-dicyanomethylethylene-2-(p-dimethylaminostyryl)-6-methyl-4H-pyran:DCM) and its derivatives. Specific examples of the phosphorescent compound include, for example, bis[2-(4,6-difluorophenyl)pyridinate]picolinate iridium (III)(bis[2-(4,6-difluorophenyl)pyridinate]picolinate iridium. (III): FIrPic), bis(1-phenylisoquinoline)(acetylacetonate)iridium(III)(bis(1-phenylisoquinoline)(acetylacetonate)iridium(III):Ir(piq) ₂ (acac)), tris( 2-phenylpyridine)iridium(III)(tris(2-phenylpyridine)iridium(III):Ir(ppy) ₃ ), tris(2-(3-p-xyyl)phenyl)pyridine iridium(III)(tris(2) Examples include iridium (Ir) complexes such as -(3-p-xylyl)phenyl)pyridine iridium (III) and TEG), osmium (Os) complexes, platinum (Pt) complexes, and the like.

The lower limit of the content of the hole transporting compound in the light emitting layer is preferably more than 20 mass% and more preferably 25 mass% or more, based on the total mass of the light emitting layer being 100 mass %. Within this range, necessary and sufficient holes are supplied to the light emitting layer, and there is an advantage that low voltage and highly efficient light emission can be obtained. Further, the upper limit of the content of the hole transporting compound in the light emitting layer is preferably 70 mass% or less, and more preferably 55 mass% or less, with the total mass of the light emitting layer being 100 mass %.

The electron transport layer 160 is formed on the light emitting layer 150. The electron transport layer 160 is a layer having a function of transporting electrons, and is formed by a vacuum evaporation method, a spin coating method, an inkjet printing method, or the like. The electron transport layer 160 may be formed to have a thickness of 15 nm or more and 50 nm or less, for example.

The electron transport layer 160 may be formed using a known electron transport material. Known electron transport materials include, for example, tris(8-quinolinolato)aluminum (tris(8-quinolinato)aluminium:Alq ₃ ), (8-hydroxyquinolinolato)lithium (lithium quinolate, (8-hydroxyquinolinolato)lithium. :Liq), a compound having a nitrogen-containing aromatic ring, and the like. Specific examples of the compound having a nitrogen-containing aromatic ring include, for example, 1,3,5-tri[(3-pyridyl)-phen-3-yl]benzene (1,3,5-tri[(3-pyridyl)). A compound containing a pyridine ring, such as -phen-3-yl]benzene, 2,4,6-tris(3'-(pyridin-3-yl)biphenyl-3-yl)-1,3,3. Compounds containing a triazine ring, such as 5-triazine (2,4,6-tris(3'-(pyridin-3-yl)biphenyl-3-yl)-1,3,5-triazine), 2 -(4-(N-phenylbenzinidazolyl-1-yl-phenyl)-9,10-dinaphthylanthracene (2-(4-(N-phenylbenzoimidazolyl-1-yl-phenyl))-9,10-dinaphthylanthracene Compounds containing an imidazole ring such as ), KLET-01, KLET-02, KLET-03, KLET-10, KLET-M1 (above, manufactured by Chemipro Kasei Co., Ltd.) and the like.

An electron injection layer 170 is formed on the electron transport layer 160. The electron injection layer 170 is a layer having a function of facilitating the injection of electrons from the second electrode 180, and is formed by using a vacuum deposition method or the like. The electron injection layer 170 may be formed to have a thickness of 0.3 nm or more and 9 nm or less, for example. As the electron injection layer 170, any material known as a material for forming the electron injection layer 170 can be used. For example, the electron injection layer 170 may include a lithium compound such as (8-hydroxyquinolinolato)lithium ((8-hydroxyquinolinato)lithium: Liq) and lithium fluoride (LiF), sodium chloride (NaCl), or fluoride. It may be formed of cesium (CsF), lithium oxide (Li ₂ O), barium oxide (BaO), or the like.

The second electrode 180 is formed on the electron injection layer 170. The second electrode 180 is specifically a cathode and is formed of a metal, an alloy, a conductive compound, or the like having a low work function. For example, the second electrode 180 may be a metal such as lithium (Li), magnesium (Mg), aluminum (Al), calcium (Ca), or aluminum-lithium (Al-Li), magnesium-indium (Mg-In), The reflective electrode may be formed of an alloy such as magnesium-silver (Mg-Ag). In addition, the second electrode 180 is a transparent conductive film such as a thin film of 20 nm or less of the above metal material, a transparent conductive film such as indium tin oxide (In ₂ O ₃ —SnO ₂ ) and indium zinc oxide (In ₂ O ₃ —ZnO). It may be formed as an electrode.

The laminated structure of the organic EL device 100 according to the present embodiment is not limited to the above example. The organic EL element 100 according to the present embodiment may be formed with another known laminated structure. For example, in the organic EL device 100, one or more layers of the hole injection layer 130, the hole transport layer 140, the electron transport layer 160, and the electron injection layer 170 may be omitted, and another layer may be additionally provided. May be provided. In addition, each layer of the organic EL element 100 may be formed as a single layer or a plurality of layers.

For example, the organic EL device 100 further includes a hole blocking layer between the hole transport layer 140 and the light emitting layer 150 in order to prevent excitons or holes from diffusing into the electron transport layer 160. Good. The hole blocking layer can be formed of, for example, an oxadiazole derivative, a triazole derivative, a phenanthroline derivative, or the like.

The present invention will be described in more detail with reference to the following examples and comparative examples, but the technical scope of the present invention is not limited to the following examples.

The structures of ET-Host, HT-Host, and WG-Host used in Examples and Comparative Examples are as shown in the chemical formulas below. In WG-Host, the value of HOMO-LUMO energy gap (Eg) is also shown.

<Preparation of organic electroluminescence device>
(Example 1)
A polymer P-1 represented by the following chemical formula was synthesized according to the method for producing Compound P described in International Publication No. 2011/159872. The number average molecular weight (Mn) of P-1 measured by gel permeation chromatography (GPC) was 141,000, and the weight average molecular weight (Mw) was 511,000.

Further, FA-14 (see the following chemical formula) described in U.S. Patent Application Publication No. 2016/0315259 was synthesized by a conventional method.

Three kinds of host compounds (ET-Host-A, HT-Host-A, WG-Host-A), and tris(2-(3-p-xyyl)phenyl)pyridine iridium (III) (TEG) which is a dopant material. (See the following chemical formula) was dissolved in methyl benzoate to prepare a coating solution for a light emitting layer (composition for forming a light emitting layer) having a solid content of 4 mass %. At this time, the mass ratio of ET-Host-A, HT-Host-A, and WG-Host-A was 1:1:1. Further, the doping amount of the dopant material was set to 10% by mass with respect to the total mass of the light emitting layer.

As the first electrode (anode), a glass substrate on which stripe-shaped indium tin oxide (ITO) was formed with a film thickness of 150 nm was prepared. PEDOT-PSS (manufactured by Sigma-Aldrich) was applied onto a glass substrate by a spin coating method so as to have a dry film thickness of 15 nm and dried to form a hole injection layer.

Next, P-1 and FA-14 were dissolved in anisole (solvent) to prepare a coating solution for hole transport layer. The content of FA-14 was 20 mass% with respect to the total mass of the hole transport layer. A hole transport layer coating solution was applied onto the hole injection layer formed above by a spin coating method and dried to form a hole transport layer having a dry film thickness of 125 nm. Next, the coating solution for a light emitting layer obtained above is applied onto the formed hole transport layer by spin coating and dried at 240° C. for 30 minutes to form a light emitting layer having a dry film thickness of 55 nm. did.

On the light-emitting layer formed above, (8-hydroxyquinolinolato)lithium (Liq) and KLET-03 (manufactured by Chemipro Kasei Co., Ltd.) were co-produced by a vacuum evaporation method so that the mass ratio was 1:1. Evaporation was performed to form an electron transport layer having a thickness of 20 nm. Next, lithium fluoride (LiF) was vapor-deposited on the electron transport layer by a vacuum vapor deposition method to form an electron injection layer having a thickness of 3.5 nm.

Aluminum (Al) was vapor-deposited on the formed electron injection layer by a vacuum vapor deposition method to form a second electrode (cathode) having a thickness of 100 nm. In this way, an organic EL device was produced.

(Examples 2-3, Comparative Examples 1-2)
An organic electroluminescence device was produced in the same manner as in Example 1 except that the content ratio by mass of the host compound was changed as shown in Table 1 below.

[Evaluation]
The luminous efficiency and the luminous lifetime of the produced organic electroluminescent element were evaluated by the following methods. The luminous efficiency was evaluated by the current efficiency (cd/A).

A predetermined voltage was applied to each organic electroluminescence element by using a direct current constant voltage power supply (manufactured by KEYENCE CORPORATION, source meter (source meter)) to cause the organic electroluminescence element to emit light. While measuring the light emission of the organic electroluminescence element with a luminance measuring device (SR-3, manufactured by Topcon Corporation), the current was gradually increased and the current was kept constant when the luminance reached 6000 nit (cd/m ² ). I left it. Here, the current value per unit area (current density) is calculated from the area of the organic electroluminescence element, and the luminance (cd/m ² ) is divided by the current density (A/m ² ) to obtain “current efficiency”. (Cd/A)" was calculated. Further, the time until the value of the luminance measured by the luminance measuring device gradually decreased to 95% of the initial luminance was defined as “LT95 life (hrs)”.

The evaluation results are shown in Table 1 below.

(Example 4, Comparative Examples 3 to 4)
An organic EL device was prepared and evaluated in the same manner as in Example 1 except that the host compound of the light emitting layer was changed to the constitution shown in Table 2 below. The evaluation results are shown in Table 2 below.

(Example 5, Comparative Examples 5-6)
An organic EL device was prepared and evaluated in the same manner as in Example 1 except that the host compound of the light emitting layer was changed to the constitution shown in Table 3 below. The evaluation results are shown in Table 3 below.

(Examples 6 to 17)
An organic EL device was produced and evaluated in the same manner as in Example 1 except that the host compound of the light emitting layer was changed to the constitution shown in Table 4 below. The evaluation results are shown in Table 3 below.

(Examples 18 to 24)
An organic EL device was prepared and evaluated in the same manner as in Example 1 except that the host compound of the light emitting layer was changed to the constitution shown in Table 5 below and the dopant material was changed to the platinum complex represented by the following chemical formula. did. The evaluation results are shown in Table 5 below.

(Example 25, Comparative Examples 7 to 8)
Examples except that the host compound of the light emitting layer was changed to the constitution shown in Table 6 below and the dopant material was changed to a red phosphorescent light emitting complex (Ir(piq) ₂ (acac)) represented by the following chemical formula: An organic EL device was produced in the same manner as in 1. The performance evaluation was performed under the condition of a brightness of 2000 nit. The evaluation results are shown in Table 6 below.

(Example 26, Comparative Example 9)
Organic compounds were prepared in the same manner as in Example 1 except that the host compound of the light emitting layer was changed to the constitution shown in Table 7 below, and the dopant material was changed to the blue phosphorescent light emitting complex (FIrPic) represented by the following chemical formula. An EL device was produced. The performance was evaluated under the condition of a brightness of 1000 nit, and the life was evaluated as the time until the initial brightness reached 70% (LT70 life (hrs)). The evaluation results are shown in Table 7 below.

(Example 27, Comparative Examples 10 to 11)
Organic compounds were prepared in the same manner as in Example 1 except that the host compound of the light emitting layer was changed to the constitution shown in Table 8 below and the dopant material was changed to the compound represented by the following chemical formula (Blue Dopant-A). An EL device was produced. Performance evaluation was performed under the condition of a brightness of 1000 nit. The evaluation results are shown in Table 8 below.

From Tables 1 to 8 above, the organic EL devices of Examples using the three types of host compounds according to the present embodiment show current efficiency (luminous efficiency) substantially equal to or higher than that of the organic EL device of Comparative Example. It was also found that the light emission life was significantly improved. Moreover, the organic EL devices of the examples showed good film-forming properties. Therefore, it was found that the host compound according to the present invention is useful as a material for an organic EL device for a coating method.

In addition, the host compound used in the examples is preferable from the viewpoint of mass production because it can form a light emitting layer of an organic EL device by a coating method.

Although the present invention has been described with reference to the exemplary embodiments and examples, the present invention is not limited to the specific exemplary embodiments and examples, and various modifications are possible within the scope of the invention described in the claims. Can be modified and changed.

100 organic electroluminescence element (organic EL element),
110 substrate,
120 first electrode,
130 hole injection layer,
140 hole transport layer,
150 light emitting layer,
160 electron transport layer,
170 electron injection layer,
180 Second electrode.

Claims (6)

An organic electroluminescence device having a light emitting layer between a pair of electrodes,
The light emitting layer is
At least one electron-transporting compound,
At least one hole transporting compound,
At least one wide gap compound having a HOMO-LUMO energy gap of 3.3 eV or more;
Including
The electron-transporting compound is a compound selected from the following compound group (1), and/or the hole-transporting compound is a compound selected from the following compound group (2), an organic electroluminescent device:


Ar in the compound group (1) and the compound group (2) is each independently a substituted or unsubstituted aryl group or a substituted or unsubstituted heteroaryl group. The organic electroluminescent device according to claim 1, wherein the wide-gap compound is a compound selected from the following compound group (3):

In the above compound group (3),
Ar _{1 s} are each independently a hydrogen atom, a substituted or unsubstituted aryl group, or a substituted or unsubstituted monovalent nitrogen-containing heterocyclic group, provided that two Ar _{1 s} are hydrogen atoms at the same time. Not,
Ar ₂ is each independently a phenyl group, a hydrocarbon ring assembly group in which a plurality of aromatic hydrocarbon rings are directly bonded by a single bond, or a substituted or unsubstituted heteroaryl group,
Ar ₃ is each independently a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heteroaryl group,
Ar ₄ is a hydrogen atom, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heteroaryl group. The light emitting layer is
The organic compound according to claim 1 or 2, comprising at least one electron transporting compound selected from the compound group (1) and at least one hole transporting compound selected from the compound group (2). Electroluminescent device. The organic electroluminescence device according to claim 1, wherein the content of the hole transporting compound in the light emitting layer is more than 25% by mass. The organic electroluminescence device according to claim 1, wherein the light emitting layer contains a fluorescent compound or a phosphorescent compound. At least one electron-transporting compound,
At least one hole transporting compound,
At least one wide gap compound having a HOMO-LUMO energy gap of 3.3 eV or more;
Solvent and
A method for manufacturing an organic electroluminescence device, comprising applying a composition containing
Production of an organic electroluminescence device, wherein the electron transporting compound is a compound selected from the following compound group (1), and/or the hole transporting compound is a compound selected from the following compound group (2) Method:


Ar in the compound group (1) and the compound group (2) is each independently a substituted or unsubstituted aryl group or a substituted or unsubstituted heteroaryl group.